I drop a comment when I appreciate a post on a site or if I have something to add to the discussion. It's caused by the sincerness displayed in the post I looked at.
And after this post RELIC-SIGHTED. I was excited enough to drop a comment

I do have 2 questions for you if it's okay. Could it be simply me or does it look as if like a few of these comments appear like written by brain dead visitors? :-P And, if you are writing on other social sites, I'd like to keep up with you.
Would you make a list every one of your social sites like your twitter feed, Facebook page or linkedin profile?